Todd Stern, a visiting lecturer at Yale Law School, was U.S. special envoy for climate change from 2009 to 2016.

As President Trump takes the reins of power, anxiety and uncertainty are the order of the day for those concerned about the threat of climate change. Trump has ranged from disbelieving (climate change is a Chinese “hoax”) to dismissive (we should “cancel” the 2015 Paris agreement) to open (“I’m looking at it very closely. . . . I have an open mind to it”) on the issue.